Triple-folded hot air sealed thermoplastic bags

ABSTRACT

A method for sealing a thermoplastic bag includes forming a first fold in a top end of the bag; forming a second fold in the top end that includes the first fold; folding the first fold to form a first portion of the first fold and a second portion of the first fold, the second portion of the first fold is folded onto the first portion of the first fold; and heat sealing the first fold and the second fold to each other and to a portion of the bag that faces the first fold, the heat sealing including applying hot air to the bag. Preferably the second fold has a height that is less than a height of the first fold such that the forming of the second fold folds the first fold to form the first and second portions of the first fold.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. application Ser. No. 14/919,022filed Oct. 21, 2015, the disclosure of which is incorporated herein bythis reference.

BACKGROUND

The present disclosure relates generally to thermoplastic packages orbags that are triple-folded and sealed by hot air to provide resistanceto insect infestation and methods for making such packages or bags.

Product packaging is important with respect to the storage of theproduct contained therein. Packages that are easy to open and enable aconsumer to easily access a product contained in the package areparticularly popular. However, the packaging should also be tightlysealed to help maintain the freshness of the product stored in thepackaging, especially with products such as comestible products or foodproducts for which product freshness and consistency is highlydesirable.

Polywoven bags can be manufactured that exhibit excellent tensilestrength qualities making them very suitable for containing a widevariety of materials. However, many closures of polywoven bags formholes in the bag that can allow insects and their larvae to enter thebag.

Grain-based insects are separated into two categories, penetrators andinvaders. Invaders are insects that typically have weakly developedmouth-parts at both the larval and adult stages. The invaders, such asIndian meal moths and red flour beetles, account for more than 75% ofthe infestations of polywoven bags. Invaders commonly enter packagesthrough openings resulting from mechanical damage, defective seals, orholes made by other insects penetrating the package. The newly hatchedlarvae of invaders typically cause the most damage because they are ableto fit through holes as small as 0.1 mm wide.

Most infestations are the result of invasion through seams and closures,and rarely through penetrations. For example, the adult saw-toothedgrain beetle has been shown to enter packaging through openings lessthan 1 mm in diameter, and the adult red flour beetle can enter holes inpackaging that are less than 1.35 mm in diameter. Many insects prefer tolay eggs in tight spaces, such as those formed when bags are folded tocreate closures. These refuges provide a safe place to lay eggs and alsogive the newly hatched larvae an ideal location to invade the packages.

Insects will take advantage of any sort of opening in a packagingmaterial in order to gain entry. These openings may form as a result ofrips, tears, or poor seals or as punctures resulting from normal wearand tear throughout the handling process. Openings in packaging may alsobe made deliberately in the form of “vents” which allow pressureequalization and air escapement deflation. These vents allow creation ofa stable pallet and avoid the bursting or shrinking of the bag duringshipment over changing altitudes. However, when an insect “smells” food,the insect will try to reach it. The vent holes are made to reducebursting and provide a means for air deflation palletizing but they alsoallow odors to escape, attracting insects and providing an access pointfor entry.

SUMMARY

In a general embodiment, the present disclosure provides a method forsealing a thermoplastic bag. The method comprises: forming a first foldin a top end of the bag; forming a second fold in the top end comprisingthe first fold; folding the first fold to form a first portion of thefirst fold and a second portion of the first fold, the second portion ofthe first fold is folded onto the first portion of the first fold; andheat sealing the first fold and the second fold to each other and to aportion of the bag that faces the first fold, the heat sealingcomprising applying hot air to the bag. This closure is generallyreferred to as a “triple-fold” throughout the present application. In analternative embodiment, the folding can be employed in combination withanother type of sealing method besides heat sealing, for exampleadhesive applied while sealing or before sealing and reactivated withheat, or taping as another example.

In an embodiment, the second fold has a height that is less than aheight of the first fold.

In an embodiment, the forming of the second fold folds the first fold toform the first and second portions of the first fold.

In an embodiment, the first portion of the first fold, the secondportion of the first fold, and the second fold are formed using only twofolding operations.

In an embodiment, the hot air is applied directly to the portion of thebag that faces the first fold.

In an embodiment, the hot air is applied directly to the first portionof the first fold.

In an embodiment, the method comprises subjecting the top end of the bagto a cooling device after the hot air has been applied.

In an embodiment, the hot air has a temperature great enough to melt thesurface of the thermoplastic material on the outside of the bag

In another embodiment, a sealed thermoplastic bag is provided by thepresent disclosure. The bag comprises: a first panel; a first foldcomprising a first portion and further comprising a second portionfolded onto the first portion, the first fold faces a portion of thefirst panel; a second fold on an opposite side of the first foldrelative to the portion of the first panel that faces the first fold;and the first portion of the first fold, the second portion of the firstfold, and the second fold have been heat sealed by hot air to each otherand to the portion of the first panel that faces the first fold.

In an embodiment, the first portion of the first fold and the secondportion of the first fold have the same top edge.

In an embodiment, the second fold and the first portion of the firstfold have the same bottom edge.

In an embodiment, the second fold and the portion of the first panelthat faces the first fold have the same top edge.

In an embodiment, the second portion of the first fold comprises abottom edge comprising an opening of the bag that is closed by the heatseal.

In an embodiment, the bag comprises vents positioned in a section of thebag selected from the group consisting of the first fold, the secondfold, the portion of the first panel that faces the first fold, andcombinations thereof. In an embodiment, at least one of the vents ispositioned at a center of the sealed thermoplastic bag such that adistance to a left side of the bag is about the same as a distance to aright side of the bag.

In an embodiment, the bag comprising gussets that connect the firstpanel to a second panel of the sealed thermoplastic bag, the secondpanel forming an opposite side of the sealed thermoplastic bag relativeto the first panel, the bag comprising vents positioned in a part of thegussets that is above a bottom edge of the first fold.

In another embodiment, a method for packaging a product is provided bythe present disclosure. The method comprises: filling the product into athermoplastic bag that comprises a first panel, a second panel oppositeto the first panel, and vents; forming a first fold in a top end of thethermoplastic bag; forming a second fold in the top end comprising thefirst fold, the second fold having a height that is less than a heightof the first fold, the first fold and the second fold are formed suchthat a portion of the first panel faces the first fold and such that atleast a portion of the vents are positioned in a section of the bagselected from the group consisting of the first fold, the second fold,the portion of the first panel that faces the first fold, andcombinations thereof; and applying hot air to the thermoplastic bag toheat seal the first fold and the second fold to each other and to theportion of the first panel that faces the first fold. In an alternativeembodiment, the folding can be employed in combination with another typeof sealing method besides heat sealing, for example adhesive appliedwhile sealing or before sealing and reactivated with heat, or taping asanother example.

In an embodiment, the bag comprises gussets that connect the first panelto the second panel, and the forming of the second fold positions aportion of the vents in a part of the gussets that is above a bottomedge of the second fold.

In an embodiment, the forming of the second fold comprises folding thefirst fold to form a first portion and a second portion of the firstfold, the second portion folded onto the first portion.

In an embodiment, the applying of the hot air comprises sealing a bottomedge of the second portion of the first fold at a position between thesecond fold and the first portion of the first fold, and the bottom edgeof the second portion of the first fold comprises an opening of the bagthat is closed by the heat seal and accessed by pulling the first andsecond folds away from the portion of the first panel that faces thefirst fold.

Thermoplastic bags of the present invention can be made of anythermoplastic material, including but not limited to, woventhermoplastic, non-woven thermoplastics, and thermoplastic coatings,lamination or adhesive on a non-thermoplastic material.

An advantage of the present disclosure is to provide an improved sealedthermoplastic bag and an improved method for making a sealedthermoplastic bag.

A further advantage of the present disclosure is to provide a tighterseal on one or both ends of a thermoplastic bag without increasing thecost per bag.

Still another advantage of the present disclosure is to provide atighter seal on one or both ends of a thermoplastic bag that meetsproduction demand requirements and quality specifications.

Yet another advantage of the present disclosure is to reduce insectinfestation and the odors that attract insects by improving the sealtightness.

Another advantage of the present disclosure is to make a package morevisually appealing while reducing product contamination by improving theseal tightness.

Yet another advantage of the present disclosure is to reduce sealcomplaints.

Another advantage of the present disclosure is to provide a moresustainable thermoplastic bag.

A further advantage of the present disclosure is to improve the sealtightness using double fold bag sealers with no loss in throughput orefficiency.

Still another advantage of the present disclosure is to provide a sealedthermoplastic bag more resistant to infestation of grain-based insects.

Still another advantage of the present disclosure is to seal athermoplastic bag without the use of additional materials (e.g. tape,adhesive) which are additional material costs for bag closing.

Yet another advantage of the present disclosure is to make the pathwayto the inside of the bag more difficult for crawling insects.

Another advantage of the present disclosure is to provide a method forfolding and sealing a bag that is not as sensitive to bag skewness ofincoming bags from a bag filler relative to other bag closing methods.

A further advantage of the present disclosure is to provide a seal thatis more air tight as compared to a double fold and seal.

Another advantage of the present disclosure is to limit or preventinsect infestation but still eliminate excessive air in the bag afterthe bag has been filled and sealed.

Yet another advantage of the present disclosure is to provide ventingthat allows removal of entrapped air in the headspace of the heat-sealedbag without creating a path to allow insect infestation, by burying thevent in the seal in such a manner that when the bag is squeezed or otherbags are stacked on the bag, the air can force its way out of the bagthrough the vent.

Additional features and advantages are described herein and will beapparent from the following Detailed Description and the Figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 2A, 3A and 4A show front perspective views of thermoplasticbags in embodiments provided by the present disclosure.

FIGS. 1B, 2B, 3B and 4B show side cross-section views of FIGS. 1A, 2A,3A and 4A, respectively.

FIG. 5 shows a front perspective view of a sealed bag provided by thepresent disclosure.

FIGS. 6A and 6B show front perspective views of a bag provided by thepresent disclosure in an unsealed configuration and a sealedconfiguration, respectively.

FIG. 7 shows a flowchart of an embodiment of a method provided by thepresent disclosure.

FIG. 8 is a schematic diagram of an exemplary device that can be used tomake an embodiment of a sealed thermoplastic bag provided by the presentdisclosure.

DETAILED DESCRIPTION

As used in this disclosure and the appended claims, the singular forms“a,” “an” and “the” include plural referents unless the context clearlydictates otherwise. The words “comprise,” “comprises” and “comprising”are to be interpreted inclusively rather than exclusively. Likewise, theterms “include,” “including” and “or” should all be construed to beinclusive, unless such a construction is clearly prohibited from thecontext. However, the devices disclosed herein may lack any element thatis not specifically disclosed. Thus, a disclosure of an embodiment usingthe term “comprising” includes a disclosure of embodiments “consistingessentially of” and “consisting of” the components identified.

FIGS. 1A and 1B show an embodiment of a package or bag 10 (hereafter“the bag 10”) that can be sealed according to the present disclosure. Inan embodiment, the bag 10 has an interior containing or capable ofcontaining a product such as, for example, human food; pet food, such ascompanion animal food, such as cat food, dog food, and the like; ornon-consumable products. The bag 10 can have a variety of sizes,capacities and shapes. In an embodiment, the bag 10 is substantiallyrectangular.

The bag 10 comprises thermoplastic material, preferably polypropylene,more preferably woven polypropylene.

The polypropylene can have many variations to the thicknesses of thedifferent layers. Many types of polymers, copolymers, inks, polymerblends, single or coextrusion lamination layers, and primers can beused. Furthermore, the polypropylene can have various weights andthreads per inch.

The polypropylene material can be made by printing the bi-axiallyoriented polypropylene (BOPP), extruding and weaving the fabric, andthen combining these two material streams together by extrusionlamination using a molten stream of a polypropylene blend that is fedthrough a slit die before the material is pinched together between twolamination rollers. Alternatively, these materials can be laminatedtogether by adhesive, especially the BOPP and a coated fabric layer.

A flattened tube of fabric can be laminated with a layer ofreverse-printed BOPP. Finished printed material can be flat and ispreferably formed into a tube by a converter before making the materialinto a bag. Simultaneously, side gussets can be placed in the tube, andthen the tube can be flush cut. Then one end of the bag can be passedthrough a bottomer which then closes one end of the bag.

As shown in FIGS. 1A and 1B, the bag 10 has a top end 11 which can beformed by a first panel 21 and a second panel 22 of the bag 10 and whichcan made of the thermoplastic material, preferably polypropylene, morepreferably_woven polypropylene. The remaining portions of the bag 10 canalso be made of the thermoplastic material, which can make the bag 10flexible. In an embodiment, the first panel 21 and the second panel 22each extend from the top end 11 to the bottom end 12 of the bag 10.

After the bag 10 is filled and sealed as discussed hereafter, the bag 10can be sold to a consumer. The consumer can open the top end 11 of thebag 10 and use an opening 15 between the first panel 21 and the secondpanel 22 to obtain at least a portion of product contained by the bag10.

The first panel 21 can be at least partially connected to the secondpanel 22 by gussets 25 connected to a first lateral side 31 and a secondlateral side 32 of the bag 10. Alternatively or additionally, the firstpanel 21 is at least partially connected directly to the second panel 22at the first lateral side 31 and the second lateral side 32 of the topend 11.

To close the bottom end 12 of the bag 10, the bottom end 12 can betriple-folded and hot air sealed as discussed with respect to the topend 11 in more detail later in this application. In an alternativeembodiment, the bottom end 12 can be double-folded and then heat sealedor taped. In another alternative embodiment, a pinch step cut can bemade in the bottom end 12 of the bag 10, and the bottom end 12 can befolded once and then heat sealed.

The top end 11 of the bag 10 can be used to fill the bag 10, for exampleafter the bottom end 12 has been closed. Alternatively or additionally,the bottom end 12 can be used to fill the bag 10 before closure of thebottom end 12. For example, the top end 11 can be sealed as discussedhereafter, then the bottom end 12 can be used to fill the bag 10, andthen the bottom end 12 can be closed. The present disclosure is notlimited to a specific way of filling the bag 10.

As shown in FIGS. 2A and 2B, an upper portion 14 of the bag 10 can betrimmed from the bag 10 to ensure that the top end 11 of the bag 10 issubstantially straight for subsequent processing. In an embodiment, thefirst panel 21 is positioned against the second panel 22 at the top end11 of the bag 10 and then the upper portion 14 of the bag 10 is trimmedfrom the bag 10. For example, the top edges of the first panel 21 andthe second panel 22 can be placed in contact across at least a majorityof the width of the bag 10, preferably across the entirety of the widthof the bag 10, and then a blade can cut the upper portion 14 from thebag 10. For example, the bag 10 can be held between rollers at aposition below the line where the bag 10 will be trimmed, and therollers can move the bag 10 past a blade that cuts the upper portion 14from the bag 10.

As shown in FIGS. 3A and 3B, a first fold 41 can be formed in the topend 11 of the bag 10. As should be clear from this disclosure, “thefirst fold 41” refers to a specific folded portion of the bag, notmerely a fold line at which the bag is folded.

The first fold 41 has a height 51, such as 1⅛ inches as a non-limitingexample. The first fold 41 can be a substantially rectangular portion ofthe bag 10 and can have lateral sides substantially parallel to thelateral sides 31, 32 of the remainder of the bag 10. The first fold 41can be formed by folding the top end 11 of the bag 10 eitherdirection—toward the first panel 21 or, instead, toward the second panel22. For illustrative purposes, the following disclosure andcorresponding figures are directed to the first fold 41 being formed byfolding the top end 11 of the bag 10 toward the first panel 21. However,one of ordinary skill will easily understand how to apply the disclosureto an embodiment in which the first fold 41 is formed by folding the topend 11 of the bag 10 toward the second panel 22. Therefore, the presentdisclosure is not limited to a specific direction by which the firstfold 41 is formed.

Any folding mechanism known to one of ordinary skill in the art can beused to form the first fold 41 in the top end 11 of the bag 10. Forexample, the top end 11 of the bag 10 can be moved through foldingplates that form the first fold 41. These folding plates can besubstantially vertical in an upward direction at a first end at whichthe top end 11 of the bag 10 enters and then, as the folding platesextend onward, the folding plates can gradually rotate 180° to besubstantially vertical in a downward direction at the second end of thefolding plates. For example, the folding plates can form a groove thatgradually rotates from substantially upward to substantially downward asthe folding plates extend from their first end at which the top end 11of the bag 10 enters. Thus the top end 11 of the bag 10 can be movedthrough the folding plates such that the first fold 41 is formed in thetop end 11 of the bag 10 by rotation of the folding plates. However, thepresent disclosure is not limited to a specific mechanism by which thefirst fold 41 is formed in the top end 11 of the bag 10.

As shown in FIGS. 4A and 4B, a second fold 42 can be formed in the topend 11 of the bag 10 comprising the first fold 41. As should be clearfrom this disclosure, “the second fold 42” refers to a specific foldedportion of the bag, not merely a fold line at which the bag is folded.

The second fold 42 is formed in the bag 10 by folding the top end 11 ofthe bag 10 in the same direction as the top end 11 of the bag 10 wasfolded to form the first fold 41. For example, if the first fold 41 wasformed by folding the top end 11 of the bag 10 toward the first panel21, the second fold 42 is formed by folding the top end 11 of the bag 10comprising the first fold 41 toward the first panel 21. If the firstfold 41 was formed by folding the top end 11 of the bag 10 toward thesecond panel 22, the second fold 42 is formed by folding the top end 11of the bag 10 comprising the first fold 41 toward the second panel 22.Preferably, the second fold 42 is a substantially rectangular portion ofthe bag 10 and has lateral sides substantially parallel to the lateralsides 31, 32 of the remainder of the bag 10 and/or substantiallyparallel to the lateral sides of the first fold 41.

The second fold 42 has a height 52 that is less than the height 51 ofthe first fold 41. As a non-limiting example, the height 51 of the firstfold 41 can be 1⅛ inches, and the height 52 of the second fold 42 can be1 inch. The height 51 of the first fold 41 and the height 52 of thesecond fold 42 each can be any distance as long as the height 52 of thesecond fold 42 is less than the height 51 of the first fold 41.

Any folding mechanism known to one of ordinary skill in the art can beused to form the second fold 42 in the top end 11 of the bag 10comprising the first fold 41. For example, the second fold 42 can beformed by moving the top end 11 of the bag 10 comprising the first fold41 through folding plates additional to any folding plates used to formthe first fold 41. These folding plates can be substantially vertical inan upward direction at a first end at which the top end 11 of the bag 10comprising the first fold 41 enters and then, as the folding platesextend onward, can gradually rotate 180° to be substantially vertical ina downward direction at the second end of the folding plates. Forexample, these folding plates can form a groove that gradually rotatesfrom substantially upward to substantially downward as the foldingplates extend from their first end at which the top end 11 of the bag 10comprising the first fold 41 enters. Thus the top end 11 of the bag 10comprising the first fold 41 can be moved through the folding platesadditional to any folding plates used to form the first fold 41 suchthat the second fold 42 is formed in the top end 11 of the bag 10.However, the present disclosure is not limited to a specific mechanismby which the second fold 42 is formed in the top end 11 of the bag 10.

As noted above, the height 52 of the second fold 42 is less than theheight 51 of the first fold 41. Thus the limited space under the secondfold 42 forces the first fold 41 to fold upon itself. As shown in FIG.4B, the first fold 41 is divided into a first portion 43 and a secondportion 44 as a result of the first fold 41 folding upon itself. Thesecond portion 44 of the first fold 41 is preferably folded onto thefirst portion 43 of the first fold 41. One or both of the first portion43 and the second portion 44 of the first fold 41 can be substantiallyrectangular portions of the bag 10 and can have lateral sidessubstantially parallel to the lateral sides 31, 32 of the remainder ofthe bag 10 and/or substantially parallel to the lateral sides of thesecond fold 42.

The first portion 43 of the first fold 41 can have a height 53 that issubstantially the same as the height 52 of the second fold 42. In suchan embodiment, the second portion 44 of the first fold 41 has a height54 that is the remainder of the height 51 of the entirety of the firstfold 41. In other words, the height 54 of the second portion 44 of thefirst fold 41 is the difference between (i) the height 51 of theentirety of the first fold 41 and (ii) the height 53 of the firstportion 43 of the first fold 41.

Preferably, the three folds, namely the first portion 43 of the firstfold 41, the second portion 44 of the first fold 41, and the second fold42 (hereafter “the folded material”) are formed in the top end 11 of thebag 10 using only two folding operations. In an alternative embodiment,three folding operations can be used, but folding thin flexiblematerials precisely into narrow folds can be very difficult and mayrequire larger folds and thus more material.

As shown in FIG. 5, the bag 10 can be sealed by hot air heat sealing thefirst portion 43 of the first fold 41, the second portion 44 of thefirst fold 41, and the second fold 42 to each other and to a portion 45of the top end 11 of the first panel 21 that faces the first fold 41.The heat sealing can be performed using a hot air impingement heatingdevice to melt the first and second folds 41, 42, 44 simultaneously withthe first panel 21 of the bag 10. For example, hot air nozzles can beinserted between the folded material and the first panel 21 of the bag10 while the bag 10 is conveyed through the hot air impingement heatingdevice. In an embodiment, the hot air nozzles are inserted between thefirst portion 43 of the first fold 41 and the portion 45 of the firstpanel 21 that faces the first fold 41. FIG. 5 shows that the bottom end12 of the bag 10 also has a triple-fold, but as noted above, the bag 10is not limited to this embodiment, and the bottom end 12 can be sealedany way known to one of ordinary skill. In one aspect, the hot air canhave a temperature great enough to melt the surface of the thermoplasticmaterial on the outside of the bag

Then the top end 11 of the bag 10 can be moved by drive rollers suchthat the molten surfaces are fused together between pinch rollers,followed by cooling of the seal area to form a permanent bond. Forexample, the fused portion of the bag 10 can be cooled by a device, suchas cooled weld rollers, after the hot air is applied. Preferably thefirst portion 43 of the first fold 41, the second portion 44 of thefirst fold 41, the second fold 42, and the portion 45 of the first panel21 that faces the first fold 41 are substantially parallel to each otherwithin the hot air heat seal.

As a result, the top end 11 of the bag 10 can be triple-folded and hotair heat sealed such that one or more of the following features can bepresent: (i) the sealed area extends all the way across the width of thebag 10, in particular along the gussets 25, if any; (ii) the bottom edgeof the sealed area is firmly sealed down; (iii) penetrating grain-basedinsects are excluded from the interior of the bag 10.

As noted above, the thermoplastic material preferably comprises a layerof BOPP.

Nevertheless, as non-limiting examples, the present inventors found thatsuitable hot air heat seals can be achieved by (i) material interfacesthat do not decrease in x and y direction strength when exposed to heat;(ii) material layers that do not lose z-direction strength when exposedto heat, such as inks and co-extrusion lamination layers; (iii)interlaminate bond strengths of 600 g/in or greater according to ASTMF904 and ISO 11339:1993.

In an alternative embodiment, the triple-fold can be employed incombination with another type of sealing method besides heat sealing,for example adhesive applied while sealing or before sealing andreactivated with heat, a heat sealable coating, ultrasonic, inductionsealing, cohesive sealing, or taping as another example.

To open the bag 10, a consumer pulls the folded material of the top end11 of the bag 10 away from the portion 45 of the first panel 21 thatfaces the first fold 41. After the bag 10 is completely unfolded, theconsumer can move the top edges of the first panel 21 and the secondpanel 22 away from each other to access the opening 15.

As shown in FIGS. 6A and 6B, vents 50 can be positioned in the foldedand sealed area of the bag 10. The shape of each of the vents 50 can bea slit, an X, a crescent, a hole, or any other shape. The vents 50 canprovide venting despite the triple-fold hot air seal that limits orprevents infestation. Air can escape through the vents by passingthrough the vents 50 in the folded area of the seal and then out of theopen ends along the lateral sides 31, 32 of the bag 10. In this regard,the air coming out from the inside of the bag 10 is under pressure and,because of its low viscosity, is able to flow out; but water cannot flowthrough the vents 50 and insects cannot force their way through thefolded material of the bag 10. In an embodiment, the vents 50 arehalf-moon shaped die cuts, but the vents 50 are not limited to anyspecific shape. Double-folded bags naturally vent because there iseffectively only one fold to hinder air escaping through the seal area,and the folded material does not have a lot of deadfold and tends to bebiased toward opening up, however this effect is decreased or eliminatedby the triple-fold of the present disclosure.

The present inventors surprisingly found that the locations of the vents50 that are depicted in FIGS. 6A and 6B, namely in the folded and sealedarea of the bag 10, are effective against insect infestation in a doubleor triple folded and sealed bag while allowing sufficient air escape.The vents 50 can be located at any location within the hot air sealedportion of the bag 10, for example in one or more locations selectedfrom (i) the portion 45 of the first panel 21 that faces the first fold41 and to which the folded material is sealed by hot air, (ii) the partof the gussets 25 that is above the bottom edge of the first and secondfolds 41,42, (iii) the first portion 43 of the first fold 41, (iv) thesecond portion 44 of the first fold 41, for example along the edge ofthe opening 15 of the bag 10, and (v) the second fold 42.

Preferably at least a portion of the vents 50 are positioned at and/orproximate to the center of the bag 10 such that these vents 50 are aboutthe same distance from the first side 31 as from the second side 32 ofthe bag 10. Alternatively or additionally, preferably at least a portionof the vents 50 are positioned in the gussets 25.

The number, shape and size of the vents 50 can vary depending on howfast the bag 10 must be vented. The location of the vents 50 can alsovary as long as the vents 50 are within the sealed part of the bag 10.

In a specific embodiment, arc vents can be positioned on a flush-cutdouble fold or triple-fold polywoven bag near the center of the bag sothat the vents do not interfere with suction cups of the baggingmachinery during production. Locating the arc vents in the middle of adouble-fold/triple-fold flush-cut bag can also have advantages of makingit difficult for grain based insect infestation to travel the long pathjourney to enter through the flap of the arc vent and reducing theamount of odor escapement that attracts the insects. Additionally thearc vents can be spaced so that after the bag is trimmed from the endand then double- or triple-folded and sealed, at a minimum one vent willbe exposed for exhausting air.

The flaps of the arc vents can be made during the bag converting processusing existing machine capabilities, such as a laser or die punch.Including the arc vents during the converting process should not reducesupplier bag line speeds, and therefore not cause additional cost to thebag. Vents could also be created before or after the bag is filled usingsuch methods as laser or die punch.

Arc vents are only one possible solution for venting in the triple-foldand seal closure. Holes or cuts of all sizes and shapes e.g.microperforations, slits, holes, and the like could all function equallywell because of the torturous path nature of the vents being placed onthe inside of the folded closure and because the location of the ventsare so far from the ends of the seals.

Without being bound by theory, the present inventors believe that thesuccess of the triple-fold and vented closure against insect infestationover the double fold and seal closure is due to the fact that thetriple-fold effectively prevents insects from squeezing in between theinner layers of the bag at the cut end of the bag being folded.Especially critical are the outside edges of the heat seal that aredirectly exposed to insects. The location of the vents is toward theinterior of the seal, within the folds, so that insects must be able totravel, squeeze and wedge themselves along a very long torturous path togain access to the interior of the package.

The triple-fold, which is a narrower seal, has the advantage that thecut edge of the bag is folded down into the nozzle heat seal area sothat it is effectively heat sealed shut. In a double-fold seal, the cutedge of the bag is still open because it is very difficult to get enoughheat along the cut edge of the bag.

As shown in FIG. 7, the present disclosure provides a method 200 forsealing a thermoplastic package or bag (“the bag”) and/or for packaginga product. In Step 202, which is optional, the product can be filledinto the bag, for example through the top end of the bag after thebottom end has been sealed. The product can be one or more foods. Forexample, the one or more foods can be one or more animal foods, such asone or more companion animal foods. In an embodiment, the foods areselected from the group consisting of canine foods, feline foods andcombinations thereof.

The bag can comprise vents that are positioned at and/or proximate tothe center of the bag such that these vents are about the same distancefrom the first side of the bag as from the second side of the bag. Thebag can comprise vents that are positioned in the gussets.

In Step 204, which is optional, an upper portion of the bag can betrimmed from the bag to ensure that the top end of the bag issubstantially straight for subsequent processing. In Step 206, a firstfold can be formed in the top end of the bag. The first fold can be asubstantially rectangular portion of the bag and can have lateral sidessubstantially parallel to the lateral sides of the remainder of the bag.In Step 208, a second fold can be formed in the top end of the bagcomprising the first fold. The second fold can be a substantiallyrectangular portion of the bag and can have lateral sides substantiallyparallel to the lateral sides of the remainder of the bag. The secondfold has a height that is shorter than the height of the first fold.Forming the second fold in the bag comprises folding the first fold uponitself to form a first portion and a second portion of the first fold,and the second portion of the first fold is preferably folded onto thefirst portion of the first fold. Preferably Steps 206 and 208 areperformed using only two folding mechanisms total.

Preferably Steps 206 and 208 are performed such that at least a portionof the vents are positioned in one or more locations selected from (i)the portion of the first panel that faces the first fold and to whichthe folded material is sealed by hot air, (ii) the part of the gussets,if any, that is above the bottom edge of the first and second folds,(iii) the first portion of the first fold, (iv) the second portion ofthe first fold, and (v) the second fold.

In Step 210, the first and second portions of the first fold and thesecond fold can be hot air sealed to each other and to the portion ofthe first panel that faces the first fold. The heat sealing can beperformed using a hot air impingement heating device to melt the firstand second folds simultaneously with the portion of the first panel thatfaces the first fold. The heat sealing can comprise inserting one morehot air nozzles between the folded material and the panel of the bagwhich the folds face, moving the top end of the bag between pinchrollers such that the molten surfaces are fused together by the pinchrollers, and the cooling the seal area to form a permanent bond. In anembodiment, the pinch rollers are cooled weld rollers. If the bagcomprises vents, preferably at least a portion of the vents arepositioned within the sealed material. In an alternative embodiment, thetriple-fold can be employed in combination with another type of sealingmethod besides heat sealing, for example adhesive applied while sealingor before sealing and reactivated with heat, or taping as anotherexample.

In an embodiment, the method comprises performing Steps 106, 108 and 110on the bottom end of the bag, before or after these steps are performedon the top end of the bag as described above.

In another aspect, the present disclosure provides a method for reducingor preventing insect infestation of a woven thermoplastic package or bag(“the bag”). The method comprises (i) optionally filling a product intothe bag; (ii) optionally trimming an upper portion of the bag from thebag; (iii) forming a first fold in the top end of the bag; (iv) forminga second fold in the top end of the bag comprising the first fold, thesecond fold having a height that is smaller than the height of the firstfold, and forming the second fold in the bag comprising folding thefirst fold upon itself to form a first portion and a second portion ofthe first fold, the second portion of the first fold preferably foldedonto the first portion of the first fold; (v) and hot air-sealing thefirst and second portions of the first fold and the second fold to eachother and to the portion of the bag that faces the first fold, forexample with a hot air impingement heating device that can comprise onemore hot air nozzles inserted between the folded material and the panelof the bag which the folded material faces and that can comprise pinchrollers that fuse the molten surfaces together. In an embodiment, themethod comprises performing steps (iii), (iv) and (v) on the bottom endof the bag, before or after these steps are performed on the top end ofthe bag as described above.

FIG. 8 is a non-limiting schematic diagram of an exemplary device 300that can be used to make any of the sealed thermoplastic bags disclosedherein, including the bag 10. The device 300 can comprise a filler 302which can fill product into a thermoplastic bag. The device 300 canfurther comprise a trimming mechanism 304 which can trim an upperportion of the bag from the bag to ensure that the top end of the bag issubstantially straight for subsequent processing. Preferably thetrimming mechanism 304 is downstream from the filler 302.

The device 300 can comprise a first folding mechanism 306 which can forma first fold in the bag, for example the first fold 41. The device 300can comprise a second folding mechanism 308 which is downstream of thefirst folding mechanism 306 and can form a second fold in the bag, forexample the second fold 42. The first and second folding mechanisms306,308 are configured such that the second fold has a height less thanthe height of the first fold. Consequently, forming the second foldcomprises folding the second fold upon itself, the first folding beingdivided into a first portion and a second portion which is folded ontothe first portion. Preferably the first and second folding mechanisms306,308 are the only folding mechanisms in the device 300 and preferablythe device 300 is configured for the bag to pass through the firstfolding mechanism 306 only once and through the second folding mechanism308 only once.

EXAMPLES

The following non-limiting examples present experimental evidence of theventing of a sealed woven thermoplastic bag while also preventinginfestation thereof as achieved by embodiments provided by the presentdisclosure.

Examples 1 and 2

The present inventors carried out two separate infestation studies onwoven polypropylene bag seals. Stored grain insect pest infestation inpackaging is defined to be when insect adults or larvae are able to gainaccess to the interior of a sealed package. The degree of infestation ismeasured by hand-counting both larvae and adult insects, and this numberis reported as the total number of insects inside the package afterexposure of the sealed package to a room filled with insects after twoweeks. The greater the number of insects that have penetrated thepackage, the less resistant to infestation are the seals.

Example 1

Forty full bags of the two types of bags were filled with 16 lbs ofpetfood. There were two different types of bags with the following sealstested: (i) double fold and tape seal, (ii) double fold and heat seal.

The bags were then exposed to thousands of each of five different typesof insects for two weeks in a chamber. After two weeks, the bags wereopened and the total number of adult and larval insects were counted byhand.

Results are shown in Table 1 and show that the double-fold heat sealedbags better resist infestation compared to typical industry doublefolded and taped bags.

TABLE 1 Woven Polypropylene Bag Total Insects Per Bag Description after2 Weeks Typical industry double folded 496 bags tape sealed on both endsDouble fold and heat 16 sealed top and bottom

Example 2

Forty each of cut in half woven bags with a particular test-sealed endwere filled with 7 lbs of petfood. Then the open end of the bag wassealed in such a way to prevent any insects from entering through thatend (i.e. the only way for the insects to enter the bag was through thetest sealed ends). The bag seals that were tested were: (i) triple-foldheat sealed without venting, (ii) triple-fold heat sealed with venting,and (iii) Heat sealed stepped pinch without venting; and (iv) Heatsealed stepped pinch with venting.

The bags were exposed to thousands of two of the most invasive insectpest varieties over two weeks, and then the bags were opened and thenumber of adult and insect larvae was counted by hand.

The results are shown in Table 2 which shows that the triple-fold sealaccording to the present disclosure, with or without venting, gave asignificantly better infestation resistant seal than other types of heatseals.

TABLE 2 Woven Polypropylene Bag Total Insects Per Bag Seal Descriptionafter 2 Weeks Triple Fold Heat seal, no vents 0 Triple Fold Heat seal,vented 0 Heat sealed stepped pinch bag, no vent 25 Heat sealed steppedpinch bag, vented 33

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present subjectmatter and without diminishing its intended advantages. It is thereforeintended that such changes and modifications be covered by the appendedclaims.

1-8. (canceled)
 9. A sealed thermoplastic bag comprising: a first panel;a first fold comprising a first portion and further comprising a secondportion folded onto the first portion, the first fold faces a portion ofthe first panel; a second fold on an opposite side of the first foldrelative to the portion of the first panel that faces the first fold;and the first portion of the first fold, the second portion of the firstfold, and the second fold have been heat sealed by hot air to each otherand to the portion of the first panel that faces the first fold.
 10. Thebag of claim 9 wherein the first portion of the first fold and thesecond portion of the first fold have the same top edge.
 11. The bag ofclaim 9 wherein the second fold and the first portion of the first foldhave the same bottom edge.
 12. The bag of claim 9 wherein the secondfold and the portion of the first panel that faces the first fold havethe same top edge.
 13. The bag of claim 9 wherein the second portion ofthe first fold comprises a bottom edge comprising an opening of the bagthat is closed by the heat seal.
 14. The bag of claim 9 comprising ventspositioned in a section of the bag selected from the group consisting ofthe first fold, the second fold, the portion of the first panel thatfaces the first fold, and combinations thereof.
 15. The bag of claim 9comprising gussets that connect the first panel to a second panel of thesealed thermoplastic bag, the second panel forming an opposite side ofthe sealed thermoplastic bag relative to the first panel, the bagcomprising vents positioned in a part of the gussets that is above abottom edge of the first fold. 16-20. (canceled)